If I were Pluto, I would be really pissed off with the astronomers that just announced the tiniest planet ever discovered. It's a new planetary system called Kepler-37, which is centered around a star similar to our sun about 210 light-years from Earth, in the constellation Lyra.

The planet, according to the observations of the Kepler telescope, "is slightly larger than our moon, measuring about one-third the size of Earth. It is smaller than Mercury."

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The discovery has been a big challenge, according to NASA's Kepler mission scientists. The detection of this tiny planet shows that they are capable of much more than they initially thought. Initially, the first exo-planets discovered were giants but, as they refined the technology and research process, they have been able to detect smaller and smaller planets. Kepler-37b—as this tiny planet is named—is now the pinnacle of this quest to detect tiny planets.

According to the astronomers at the Jet Propulsion Laboratory, "while the star in Kepler-37 may be similar to our sun, the system appears quite unlike the solar system in which we live."

Astronomers think Kepler-37b does not have an atmosphere and cannot support life as we know it. The tiny planet almost certainly is rocky in composition. Kepler-37c, the closer neighboring planet, is slightly smaller than Venus, measuring almost three-quarters the size of Earth. Kepler-37d, the farther planet, is twice the size of Earth.

The importance of the this discovery

But there's more to this discovery than just a quest to search smaller planetary bodies. Jack Lissauer—planetary scientist at NASA's Ames Research Center in Moffett Field, California—say that Kepler-37d "suggests such little planets are common, and more planetary wonders await as we continue to gather and analyze additional data." Thomas Barclay—lead author of the study and Kepler scientist at the Bay Area Environmental Research Institute in Sonoma, California—agrees:

We uncovered a planet smaller than any in our solar system orbiting one of the few stars that is both bright and quiet, where signal detection was possible. This discovery shows close-in planets can be smaller, as well as much larger, than planets orbiting our sun.

Great news, people. But Pluto—which was expelled from the list of planets in our solar system in August 24, 2006—is still crying in a corner. [NASA via Popular Science]